Date: Monday 18-Sep-2023
Speaker: Cauê Borlina
Title: Understanding the Evolution of the Early Solar System through Paleomagnetism of Meteorites
Abstract: Magnetic records from meteorites and their components can provide important information about the evolution and architecture of the early solar system. That is because large-scale magnetic fields and gas are coupled in protoplanetary disks. In this talk, I will present how we can use micro-paleomagnetism to obtain magnetic records from 100 µm-sized meteoritic inclusions (i.e., calcium-aluminum-rich inclusions and chondrules) to obtain constraints on the evolution of the early solar system. I will discuss how (1) the magnetic records from calcium-aluminum-rich inclusions point to the presence of magnetized disk winds and/or stellar outbursts during the very beginning of the solar system and (2) the magnetic records from chondrules suggest the presence of a disk substructure a few million years later. These results provide information about mechanisms that drove mass and angular momentum during the protoplanetary disk phase of the solar system, and how chemical reservoirs were kept apart during that time. In turn, learning how our solar system evolved can help us understand how planetary systems form elsewhere.
Date: Monday 25-September-2023
Speaker: Jake Turner
Title: The ongoing hunt to detect radio emission from the Tau Bootis exoplanetary system
Abstract: One of the most important properties of exoplanets has not yet been directly detected despite decades of searching: the presence of a magnetic field. Observations of an exoplanet’s magnetic field would yield constraints on its planetary properties that are difficult to study, such as its interior structure, atmospheric escape and dynamics, and any star-planet interactions. The presence of magnetic fields on gas giants also affects the understanding of their origins and evolution. Additionally, magnetic fields may contribute to the habitability of terrestrial exoplanets. Observing planetary auroral radio emission is the most promising method to detect exoplanetary magnetic fields. In this talk, I will present our recent study of the Tau Bootis exoplanetary system where we have the first possible detection of an exoplanet in the radio using LOFAR (Turner et al. 2021). Assuming the emission is from the planet, we derived a maximum surface polar magnetic field for tau Boo b between ~5-11 G. The magnetic field and emission strengths we derived are consistent with theoretical predictions, and if this detection is confirmed it will place important constraints on dynamo theory, comparative planetology, and exoplanetary science in general. Additionally, I will present the first results of an extensive multi-site follow-up campaign to confirm the radio detection of tau Boo b. Our first observing campaign consists of low-frequency radio data taken simultaneously from NenuFAR and LOFAR. Preliminary analysis of this data show no signs of emission. Therefore, the original signal may have been caused by an unknown systemic or we are observing variability in the planetary radio flux due to observing at different parts of the stellar magnetic cycle. Our second follow-up observing campaign is designed to test the latter conclusion. We have coordinated observations of the magnetic maps of the host star alongside many months of intensive radio monitoring by NenuFAR. Preliminary results on the second campaign will be presented. Finally, I will briefly highlight the promising landscape of studying exoplanetary magnetic fields in the coming decades with future ground- and space-based radio telescopes.
Date: Monday 09-Oct-2023
Speaker: Raphael Marschall (Observatoire de la Côte d'Azur)
Title: What we know about the formation and evolution of the protoplanetary disk of our Solar System
Abstract: Understanding the formation and evolution of the protoplanetary disk is a prerequisite to understanding planetesimal formation. The latter is an essential step to understanding planet formation. The distribution of these first solid bodies will drive the locations where planetary embryos can grow, eventually leading to fully-fledged planets. For the Solar System, a given disk formation and evolution model needs to meet at least the following three criteria:
1. It must produce an extended gas and dust disk (e.g., ~45 au for the dust).
2. Within the disk, the local dust-to-gas ratio in at least two distinct locations must sufficiently increase to explain the early formation of the parent bodies of non-carbonaceous (NC) and carbonaceous (CC) iron meteorite.
3.Dust particles, which have condensed at high temperatures (i.e., CAIs), must be transported to the outer disk.
Recent 1D disk models tracking the evolution of disk and planetesimal formation can satisfy criteria 2 & 3 but not 1. Their disks extend only slightly beyond the water snowline (~5 au) because of the rapid dust growth beyond the snowline and subsequent drift back towards the proto-star due to aerodynamic drag in the tangential direction. Models where material falls into the disk at large distances naturally satisfy criteria 1 and, in some cases, 2 but not 3. Here I will show that an initial rapid expansion -- forming an inflationary disk stage -- can satisfy all three conditions.
Date: Monday 16-Oct-2023
Speaker: Matthew Nixon (UMD)
Title: Marginalising over the competition: Robust atmospheric inference in the face of multiple candidate models
Abstract: A key goal of exoplanet spectroscopy is to measure atmospheric properties, such as abundances of chemical species, in order to connect them to our understanding of atmospheric physics and planet formation. In this new era of high-quality JWST data, it is paramount that these measurement methods are robust. When comparing atmospheric models to observations, multiple candidate models may produce reasonable fits to the data. Typically, conclusions are reached by selecting the best-performing model according to some metric. This ignores model uncertainty in favour of specific model assumptions, potentially leading to measured atmospheric properties that are overconfident and/or incorrect. In this talk, I will discuss ensemble methods for addressing model uncertainty by combining posterior distributions from multiple analyses. These methods lead to uncertainties on retrieved parameters that are larger, but more realistic given our modelling capabilities. I will show an application to HST data of a hot Jupiter which demonstrates that uncertainties derived from retrievals of HST spectra have likely been underreported. These methods are widely applicable to other exoplanet analysis processes, such as combining results from different data reductions.
Date: Monday 23-Oct-2023
Speaker: Ludmilla Kolokolova (UMD)
Title: Large dust particles in the Solar system and beyond
Abstract: Recent observations of different dusty objects (debris disks, comets, active asteroids) show an abundance of dust particles in the size range of hundreds of microns, millimeters, and even centimeters.
Evidence of this is not only in situ data for comets and asteroids but also unusual photometric and polarimetric properties of some objects, including debris disks. Specifically, their phase curves are very different from those considered typical for cosmic dust. I consider laboratory measurements and computer modeling, which not only proved that unusual phase curves indicate the large size of the observed dust particles but also allow estimation of their composition and structure.
I present photopolarimetric observations of comet C/2014 B1 (Schwartz) at 9.6 au, active asteroid (248370) QN173, and DART ejecta, and show how computer modeling allows us to characterize large dust particles in these objects and variations of their properties with time and within the objects.
Date: Monday 30-Oct-2023
Speaker: Stavro Ivanovski (INAF)
Title: Dust dynamics in expanding flow in different small bodies environments
Abstract: I will review the dust dynamics studies in two small bodies environments – one in the vicinity of a comet 67P and another one of the vicinities of Dimorphos after the impact of the DART spacecraft. The focus will be the similarity of the rotational motion of dust particles in the inner atmospheres of comets and whether we can derive such similarity in the ejecta plume dynamics after the impact on asteroid.
In-situ measurements of individual dust grain parameters in the immediate vicinity of a cometary nucleus are being carried by the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko. For interpretation of these observational data, a model of dust grain motion as realistic as possible is requested. In particular, the results of Stardust mission and analysis of samples of interplanetary dust have shown that these particles are highly non-spherical. In many cases precise simulations of non-spherical grain’s dynamics is either impossible or computationally too expensive. I will present the derivation of scaling laws of rotational motion applicable for any shape of particles, using a set of universal, dimensionless parameters characterizing the dust motion in the inner cometary coma. The scaling relations for translational and rotational motion of dust grains in a cometary environment are proposed.
In the second part of my talk, I will present latest results on advancements on the reconstruction of the dust dynamics of the plume formed after the NASA’s Double Asteroid Redirection Test (DART) impact, the first space mission that successfully demonstrated the kinetic impactor technique more than a year ago. ASI’s Light Italian Cubesat for Imaging of Asteroids (LICIACube) was the first Cubesat to image this plume. The DART impact into Dimorphos caused ejecta plume propagation with high velocity and very filamentary structure, composed of dust particles from μm to cm sizes in size. To estimate the size distribution and velocity distribution of the plume in close vicinity to Dimorphos, captured in the LICIACube images is still unanswered question. A 3D+t model was used to compute single particle trajectories, the dust rotational frequencies and velocity as well as the particle orientation at any time and distance. The role of the fragmentation of the particles has been addressed for reconstruction of the plume structure.
Date: Monday 06-Nov-2023
Speaker: Ben Sharkey (UMD)
Title: What are Jupiter's irregular satellites? Testing Giant Planet Migration with JWST
Abstract: Jupiter's irregular satellites are small bodies thought to be captured from the hypothesized era of planet migration. Models of the formation and migration of giant planets predict that these small satellites were likely captured from the primordial Kuiper Belt. Placing constraints on their material composition(s) is critical to test whether irregular satellites share lineages with other captured populations (i.e., Jovian Trojan asteroids) and present-day Kuiper Belt objects. I will discuss the JWST Cycle 2 program I am leading to address these questions, with particular attention to how the unique collisional environment of irregular satellites may provide fundamental insights into the evolution of dark, carbonaceous surfaces.
Date: Monday 13-Nov-2023
Speaker: Shubham Kanodia (Carnegie EPL)
Title: Searching for GEMS – Giant Exoplanets around M-dwarf Stars
Abstract: Giant (gaseous) exoplanets around M-dwarf stars (GEMS) represent an extreme of planet formation, attributed to the theorized difficulty in forming them. I will share preliminary results from the Searching for Giant Exoplanets around M-dwarf Stars survey, which includes a sample of a million M-dwarfs, and is expected to find 50–100 transiting GEMS while providing accurate estimates of their occurrence as a function of stellar mass. I will discuss how this sample has started to challenge our understanding of giant planet formation around low-mass stars and discuss exciting new trends in giant planet bulk properties across different samples. I will also present new results exploring gravitational instability as a means of rapid GEMS formation. Finally, I will discuss future prospects and the potential of this sample, including our JWST Cycle 2 program to study 7 GEMS, characterize their atmospheres, and determine their bulk metallicity.
Date: Monday 27-Nov-2023
Speaker: Quentin Changeat (STScI)
Title: Towards population studies of exoplanet atmospheres
Abstract: With NASA/ESA/CSA-JWST and ESA-Ariel, we are entering a new era of exoplanetary science. In the next decade, those revolutionary observatories will obtain high quality spectroscopic data for thousands of exoplanets, shifting our focus from the detection of other worlds to their characterization. Sucessfully characterizing a wide range of exoplanets will allow us to infer trends and answer major questions in our field: what are exoplanets made of? how do they form? In this presentation, I will discuss the challenges associated with the analysis of such extensive datasets, also highlighting key outcomes from population studies that have used previous instruments.
Date: Monday 04-Dec-2023
Speaker: Katie Bennett (JHU)
Title: Searching for M-Dwarf Rocky Planet Atmospheres with HST and JWST
Abstract: Which rocky exoplanets have atmospheres, and which do not? This presumably simply question is the first that must be answered in the pathway toward understanding the prevalence of habitable planets in our Galaxy. The exoplanet community has focused on answering this question for rocky planets orbiting M-dwarfs, as these planets orbit the smallest and coolest stars and therefore are the most amenable to characterization. However, the question of whether exoplanet atmospheres can endure in the close-in, high-energy environment of M-dwarf stars remains almost entirely unknown from an observational standpoint. In this talk, I discuss our efforts to uncover whether two nearby M-dwarf rocky planets have atmospheres: GJ 1132b and LTT 1445Ab. Two near-infrared transits of GJ 1132b were observed with the James Webb Space Telescope (JWST), and one near-infrared transit of LTT 1445Ab was observed with the Hubble Space Telescope (HST). I will bring us on a journey through the data reduction process, discussing the ongoing challenges of searching for small signals and comparing the use of HST and JWST in this endeavor. I discuss what we have (and have not) learned about these two planets and lessons learned for future rocky exoplanet observations.
Date: Monday 11-December-2023
Speaker: Carol Souza-Feliciano
Title: TBD
Abstract: TBD
For further information contact PALS coordinator Jacob Kloos at jlkloos@umd.edu.
